A. c. power supply for rate gyro

ABSTRACT

A full wave transformerless A.C. power supply for the spin motor of a rate gyro, comprising driver amplifiers and bridge switching circuits controlled by a frequency-determining oscillator, inverting a D.C. power signal to generate an A.C. drive signal for the rate gyro spin motor without appreciable loading of the power supply.

United States Patent Van Dyke et al. 1 1 March 6, W73

[ A. C. POWER SUPPLY FOR RATE [56] References Cited Y G R0 UNITED STATES PATENTS [75] Inventors: John Van Dyke, Byron Center, 3 416057 12/1968 F d t 1 /1 1 X my 6 a. it??? Lamfers Jemson both of 3,343,063 9/1967 Keeney, Jr. et al ..318/l7l x 3,346,796 10/1967 Avey ..3l8/227 x Assignee: R. C. Inc., Grand Rapids, Mich.

Filed: Oct. 16, 1970 Appl. No.: 81,417

Related US. Application Data Division of Ser. No. 794,018, Jan. 27, 1969.

1111. c1. ..H02p 5/40 Field of Search ..3l8/l38, 171, 227, 230, 231, 318/341 Primary ExaminerGene Z. Rubinson Attorneyl ,loyd L. Zickert A full wave transformerless A.C. power supply for the spin motor of a rate gyro, comprising driver amplifiers and bridge switching circuits controlled by a frequency-determining oscillator, inverting a DC. power signal to generate an AC. drive signal for the rate gyro spin motor without appreciable loading of the power supply.

ABSTRACT 4 Claims, 2 Drawing Figures AAAAAp AAAAA A. C. POWER SUPPLY FOR RATE GYRO CROSS REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 794,018, filed Jan. 27, 1969.

BACKGROUND OF THE INVENTION Rate gyros, and particularly those used in aircraft instrumentation, present stringent operational requirements arising partly from the adverse conditions under which they may be required to operate. For example, the electrical control and indicator system for a rate gyro may be required to function under extreme temperature variations. The conditions that produce a major temperature change may correspond with operating conditions that require the utmost accuracy from the rate gyro, particularly when the aircraft is in operational difficulty.

Nevertheless, the rate gyro and its electrical control and indicator system must be maintained at a minimum in size. The increasing complexity of aircraft instrumentation and the limited space available places a substantial premium on size reduction for any part of the overall instrumentation, including the rate gyro. Transformers and other inductive components in the control and indicator system are undesirable because they may radiate electromagnetic fields that can interfere with the operation of other adjacent instrumentation systems. Furthermore, inductive components tend to be bulky and limit the size reductions that can be accomplished in the overall system.

Ideally, the electrical control and indicator system for a rate gyro should be of minimum size and preferably should be based entirely upon solid state components to afford maximum ruggedness and reliability. Power losses in the system should be held to a minimum; that is, efiiciency of the overall system should be maintained as high as possible to minimize the load on the electrical system of the aircraft. Transformers and other inductive components are preferably avoided whenever possible. The rate gyro should come up to synchronous speed as rapidly as possible and should afford maximum torque, from the spin motor, whenever the rotational speed is reduced to any appreciable extent.

SUMMARY OF THE INVENTION It is a principal object of the invention, therefore, to provide a new and improved electrical control and indicator system for a rate gyro employing an A.C. spin motor energized from a D.C. power supply, in which the start control circuit, the inverter power supply, and the demodulator are all combined in a single integrated circuit of minimum size requiring minimum power for highly efficient operation.

A more specific object of the invention is to afford a full-wave transformerless A.C. power supply for the spin motor of a rate gyro which requires no inductive components and which affords full wave energization of the motor with losses limited to the saturation voltages of solid state switching devices incorporated in the inverter circuit of the power supply.

Accordingly, the present invention is directed to a full-wave transformerless A.C. power supply for the spin motor of a rate gyro, comprising a D.C. power supply and an oscillator for generating an initial A.C. signal of given frequency. The power supply further comprises a pair of driver amplifiers each including a semiconductor switching device; and means for applying the initial A.C. signal to the driver amplifiers to develop two synchronous A.C. drive signals of substantially rectangular waveform, at the aforementioned given frequency. A pair of bridge switching circuits are included in the power supply; each includes a first semiconductor switching device connected to one terminal of the D.C. power supply, a complementary semiconductor switching device connected to the other terminal of the D.C. power supply, and an output terminal connected to both switching devices and to one field winding of the rate gyro spin motor. Means are provided for applying each of the drive signals to one of the bridge switching circuits to develop a full-wave output signal of generally rectangular waveform at the output terminals, thus energizing the motor.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be made as desired by those skilled in the art without departing from the present invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a rate gyro, partly schematic, constructed in accordance with one embodiment of the invention; and

FIG. 2 is a detailed schematic diagram of a rate gyro system corresponding to that of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The electrical control and indicator system for a rate gyro that is illustrated in FIG. ll includes a synchronous A.C. spin motor 10, comprising three field windings 11A, 11B and 111C inductively coupled to a rotor 12. Motor 10 is preferably a hysteresis motor, but may constitute any other desired form of motor suitable for use in a rate gyro. Though windings 1 lA-l 1C are shown in a Y-connection, a delta connection can be used if desired. A two-winding motor can also be employed.

Motor windings 111A and 11B are electrically connected to an A.C. supply constituting an inverter circuit l5. Inverter 15 is energized from an appropriate D.C. supply at terminals 8+ and B. For convenience in illustration of the circuit, the 3- terminal is shown as constituting system ground.

In the circuit of FIG. I, winding 11C, the third field winding of motor 10, is utilized in a manner essentially similar to a starting winding for a single phase motor. A fixed capacitor 82 is connected from the input terminal of winding 1 11C to the A.C. supply, inverter 15, the connection being made at the same inverter terminal as is connected to winding 11B. A starting capacitor 81 is incorporated in a motor starting circuit, in parallel with capacitor 82. But the starting circuit comprising capacitor 811 extends through a start control 13 that is utilized to disconnect capacitor 81 from motor winding 11C under running conditions, as generally illustrated by the contacts 21 in series with capacitor 81.

The rate gyro system of FIG. 1 further includes a pick-off transformer 18 for the gyro. Transformer 18 may be of conventional construction and is shown to include a primary winding 18A and two secondary windings 18B and 18C connected to each other at a canter terminal 103. The construction of the pick-off transformer is such that the coupling from primary winding 18A to the two secondaries 18B and 18C is uniform and equal when the gyro is subject to no angular velocity or rate input. When the gyro is subject to an angular velocity, the coupling from the primary winding of the transformer to the two secondaries becomes unbalanced to indicate both the direction and the amplitude of the input turn rate to which the gyro is subjected. Thus, the A.C. signals induced in windings 18B and 18C constitute an analog of the turn rate to which the gyro is subjected.

It should be understood that the illustration of pickoff transformer 18, in FIGS. 1 and 2, is substantially simplified from the physical construction actually employed. The pickoff may, for example, comprise a series of variable transformers inductively coupled to a rotor of irregular shape; rotation of the rotor increases coupling in some of the transformers and decreases coupling in others. But the basic operation can be readily understood from the three-winding construction illustrated.

An input signal to pickoff transformer 18 is supplied from a multi-vibrator 16 that is electrically connected to the primary winding 18A of the pickoff transformer. Winding 18A is returned to the positive terminal of a DC. voltage regulator 19. Voltage regulator 19 also serves as a power supply for start control 13 and for a demodulator 17. Demodulator 17 is coupled to the secondary windings of the pickoff transformer 18 and drives an appropriate rate-indicating instrument or instruments as illustrated by the devices 20A and 208 in FIG. '1. The number of indicating instruments required is dependent upon the instrumentation system in which the rate gyro is incorporated; in a typical aircraft application, two such instruments may be used.

Considering briefly the operation of the rate gyro system illustrated in FIG. 1, it is seen that spin motor 12 is energized from inverter 15. When the system is first placed in operation, the voltage across motor winding 11C is sensed in start control 13. Under starting conditions, this voltage is quite low; as long as the low-voltage condition continues, the start control maintains switch 21 closed and thus couples starting capacitor 81 into the motorcircuit. The addition of starting capacitor 81 in parallel with running capacitor 82 affords increased starting torque for spin motor and enables the spin motor to reach its synchronous speed more rapidly than would otherwise be possible.

As spin motor 10 nears synchronous speed, the voltage across the motor winding llC connected to start control 13 increases markedly. This increased voltage is sensed in start control 13 and is employed to open the switch 21 and thus disconnect starting capacitor 81 from the motor circuit. For normal running conditions, therefore, capacitor 81 is not utilized in the motor circuit. This permits realization of the optimum synchronous torque for motor 10.

5 ject to no angular velocity, the A.C. analog signals induced in secondary windings 18B and 18C of pickoff transformer 18 are equal in amplitude. Under these conditions, the output signal from the demodulator is zero and the indicating instruments 20A and 208 show a zero-rate performance.

Whenever a turn rate is applied to the gyro, a differential in amplitude is developed, between the A.C. analog signals induced in windings 18B and 18C of the pickofi transformer, which is proportional to the turn rate. This signal differential is demodulated, detected and amplified in demodulator 17, producing a DC. analog signal having an amplitude proportional to the turn rate and a polarity representative of the direction of the turn rate. It is this D.C. analog signal that is supplied to indicators 20A and 20B to afford a positive indication of the angular velocity (turn rate) to which the gyro is subject.

In the specific circuit arrangement for the rate gyro system that is shown in FIG. 2, the switching device 21 of start circuit 13 (FIG. 1) is shown to comprise a triac 21A. A triac is a bilaterally conductive signal-controlled semiconductor switch; as used in this application it is intended to include any other operationally similar semiconductor device such as a quadrac, etc. One of the main input-output electrodes of the triac is connected to starting capacitor 81 and the other main electrode is connected back to the motor circuit and specifically to motor winding 11B. The gate electrode of the triac is connected to the collector of a gate transistor 22 through a diode 71; a resistor 42 is connected in parallel with diode 71. The emitter of transistor 22 is connected to the emitter of an auxiliary gate transistor 23; the emitters of transistors 22 and 23 are returned to system ground through a resistor 45. The base of transistor 22 is connected to the collector of transistor 23 and is also connected through a resistor 43 to the positive tenninal 14 of the DC voltage regulator 19.

The base of the auxiliary gate transistor 23 is connected in a sensing circuit that senses the operating voltage of motor winding 1 1C. This sensing circuit is a voltage divider that includes, in series, beginning at the external terminal of winding 1 1C, a resistor 41, a diode 72, and a resistor 46 that is returned to system ground. A resistor 44 is connected from the base of transistor 23 to the common terminal between diode 72 and resistor 46 in the sensing circuit.

Voltage regulator 19 comprises two transistors 24 and 25, preferably silicon power transistors. The emitter of transistor 24 is connected to the B- supply, here taken as system ground. The base of transistor 24 is connected to a resistor 49 which is returned to the B- terminal. The collector of transistor 24 is connected to the base of transistor 25 and is also connected to the B+ supply by a resistor 47.

The collector of transistor 25, in voltage regulator 19, is connected to the B+ supply terminal. The emitter of transistor 25 is connected to the base of transistor 24 through three cascaded zener diodes 73, 74 and 75 affording a voltage reference. The emitter of transistor 25 is also connected to the terminal 14 that constitutes the positive-polarity output terminal of the voltage regulator. In a typical operating circuit, regulator 19 restricts voltage changes at terminal 14 to less than 1 percent over an input range of more than 35 percent (e.g., 21 to 29 volts).

The operating circuit for the inverter 15, as shown in FIG. 2, comprises two silicon bilateral switches 30 and 31. These silicon bilateral switches, sometimes referred to hereinafter by the designation SBS, each constitute a planar silicon monolithic integrated circuit having the electrical characteristics of a bilateral thyristor. These devices are capable of switching at relatively low voltages and are characterized by a very low temperature coefficient, affording high stability of switching voltage over a wide temperature range, as may be necessary in many applications including aircraft instrumentation.

The input to inverter 15 is derived from voltage regulator 19. The positive-polarity terminal 14 of the voltage regulator is connected through a resistor 50 to two parallel input resistors 52 and 53 that are in turn connected to the SBS devices 30 and 31, respectively. A capacitor 86 is connected across resistors 52 and 53; capacitor 86 and the two resistors 52, 53 afford a frequency-determining circuit for the inverter. SBS 30 is returned to system ground (13-) through a zener diode 76 and SBS 31 is returned to system ground through a zener diode 77. This affords an oscillator constituting a self-commutating flip-flop circuit, having output terminals 90 and 91, in which SBS 30 and SBS 31 fire alternately. When one SBS fires, the other SBS is cut off by the current through capacitor 86, which causes an instantaneous voltage change at the anode of the other device.

inverter 15 further comprises a driver amplifier stage including two transistors 28 and 32. The base of transistor 28 is connected to the oscillator output terminal 90. The emitter of transistor 28 is returned to system ground. The collector is connected to the input terminal 92 of a bridge-like switching circuit 94. Similarly, the base of the amplifier transistor 32 is connected to the oscillator output terminal 91. The emitter of transistor 32 is connected to system ground and the collector is connected to an input terminal 93 of a bridge switching circuit 95.

The switching bridge 94 includes two complementary transistors 26 and 27, each having its base connected to input terminal 92. The emitters of transistors 26 and 29 are connected to each other and to an output terminal 96 that is connected to motor winding 11A. The collector of transistor 29 is returned to system ground and the collector of transistor 26 is returned to the 13+ supply. The bases of transistors 26 and 29 are also connected to the B+ supply through a resistor 48.

A similar arrangement is utilized in the other bridge switching circuit 95, which comprises two complementary transistors 27 and 33. The bases of transistors 27 and 33 are connected to each other at terminal 93, which is connected to the B+ supply through a resistor 51. The collector of transistor 27 is connected to 13+ and the collector of transistor 33 is connected to B- (system ground). The emitters of transistors 27 and 33 are connected together at an output terminal 97 that is connected to motor winding 11B.

Multivibrator 16, in the construction illustrated in FIG. 2, comprises two transistors 36 and 38. The base of transistor 36 is connected to a resistor 56 that is returned to system ground. The emitter of transistor 36 is connected to a resistor 57 that is returned to system ground. The emitter of transistor 36 is also connected to a capacitor 84 that is in turn connected to an output terminal 98. Output terminal 98 is connected to one terminal of the primary winding 18A of pickoff transformer 18, winding 18A having its other terminal connected to the positive-polarity output terminal 14 of voltage regulator 19. The base electrode of transistor 36 is also connected to output terminal 98 through a resistor 60.

The collector of transistor 36 in multivibrator 16 is connected through a resistor 61 to the base of transistor 38. The collector of transistor 38 is connected to system ground. The emitter of this transistor is directly connected to the output terminal 98 for the multivibrator.

Demodulator 17 is a balanced self-rectifying differential amplifier. It comprises two amplifier transistors 34 and 39 and two switching transistors 35 and 37, sometimes referred to hereinafter as load transistors. The base of amplifier transistor 34 is connected to the end terminal 101 of the secondary winding 18B of pickoff transformer 18. The collector of transistor 34 is connected through a resistor 54 to the positive-polarity terminal 14 of voltage regulator 19. The emitter of transistor 34 is connected to one output terminal 195 for the demodulator, terminal 105 in turn being connected to the instrument load for the rate gyro, represented in FIG. 2 by the single resistor 20.

Amplifier transistor 39, in demodulator 17, has its base connected to the end terminal 102 of the secondary winding 18C of pickoff 18. 28. The collector of transistor 39 is connected through a resistor 55 to the regulated positive-polarity supply terminal 14. The emitter of transistor 39 is connected to a second output terminal 106 for the demodulator circuit, terminal 106 being connected to load 26. A filter capacitor 83 is connected across the output terminals 105 and 106 of the demodulator.

In addition to the connections described above, the emitter of amplifier transistor 34 is connected to the collector of its load transistor 35 and, through a resistor 58, to the base of the other load transistor 37. Similarly, the emitter of amplifier transistor 39 is electrically connected to the collector of its load transistor 37 and is connected through a resistor 62 to the base of the other load transistor 35. The emitters of load transistors 35 and 37 are electrically connected to each other and are returned to system ground (13-). The demodulator circuit is completed by a bias resistor 59 that connects the common center terminal 103 of the secondary windings 18B and 18C of pickoff transformer 18 back to system ground. A smoothing capacitor is connected across the transformer output terminals 101 and 102.

In considering the operation of the rate gyro system of FIG. 2, perhaps the best starting point is the A.C. power supply for spin motor 10, inverter 15. The initial stage of the inverter is the oscillator comprising SBS devices 30 and 31, resistors 52 and 53, diodes 76 and 77, and capacitor 86. As noted above, each SBS becomes conductive at a given fixed voltage. The circuit functions as a free-running multivibrator, operating at a frequency determined by the impedances of the resistors 52 and 53 and the capacitor 86. Each of the zener diodes 76 and 77 provides a stable break-over voltage for the respective SBS device to which it is connected. Furthermore, the zener diodes provide clamping for transistors 28 and 32 in the buffer amplifier or driver stage of the inverter. The circuit illustrated affords high frequency stability over wide ranges of ambient temperature, the frequency variation being less than percent over a range from 5 5 to +1 00C.

The output signal from the oscillator, in inverter 15, is a signal of rectangular waveform that switches the driver transistors 28 and 32 between conduction and cut off in alternation with each other. Actuation of the driver transistors between conduction and cut-off produces two synchronous A.C. drive signals of substantially rectangular waveform, displaced 180 in phase from each other. These A.C. drive signals actuate the bridge switching circuits 94 and 95 connected to the windings 11A and 11B of spin motor 10.

Thus, in any half cycle of the oscillator in which driver transistor 28 is driven to conduction, the positive voltage at input terminal 92 is reduced materially by the drop across resistor 48, effectively applying a negative-going signal to the base electrode of each of the switching transistors 29 and 26. As a consequence, transistor 26 is driven to cut-off and the complementary transistor 29 is driven to saturated conductive condition. With transistor 26 conductive and transistor 29 cut off, a negative-going pulse is effectively supplied to motor winding 11A. That is, winding 11B is effectively connected to the 8- supply (system ground) through transistor 29.

In the same half cycle in which transistor 28 is driven conductive, the other driver transistor 32 is cut off. When this occurs, the instantaneous positive voltage at terminal 93 increases materially, since there is now no appreciable current through resistor 51, effectively applying a positive-going signal to the base electrode of each of the transistors 27 and 33. Consequently, transistor 27 is driven conductive and transistor 33 is cut off. Accordingly, a positive polarity connection is made from 13+ through transistor 27 to motor winding 1 1B, completing a circuit for energization of the motor windings.

On the next half cycle, the driver transistors 28 and 32 are reversed in their operating conditions. That is, driver transistor 28, in the next half cycle, is driven to cut off and driver transistor 32 is driven conductive. This produces a positive-going signal at the bridge input terminal 92 and a negative-going signal at the bridge input terminal 93. In consequence, switching transistors 27 and 29 are driven to cut off and switching transistors 26 and 33 are driven to conductive condition, supplying an energizing signal of opposite polarity to motor windings 1 1A and 118 byreversing the effective connections to the motor windings from 3+ and B. In each half cycle of the inverter operation, therefore, the transistors pairs 27, 29 and 26, 33 are driven conductive in alternation, supplying a full wave alternating current of rectangular waveform to spin motor 10.

Inverter affords several advantages with respect to previously known circuit arrangements. There are no transformers or other inductive components required to accomplish the requisite switching action for energizing the motor with the required A.C.current. The particular driver and switching circuits employed eliminate loading of the free-running multivibrator that constitutes the initial oscillator stage of the inverter. With full wave switching, the losses in the inverter are quite low, being limited to the saturation voltages of the transistors. Moreover, an excellent impedance match is readily obtained between the high impedance of the driver circuits comprising transistors 28 and 32 and the low impedance of motor 10. The use of the complementarily symmetrical bridge circuits 94, in the output of the inverter is of particular advantage because it permits operation from a single collector voltage source, the B+ supply, while retaining the many advantages noted above. Temperature variations are effectively eliminated.

Operation of the remainder of the system will be described only briefly, since it is the power supply that constitutes the subject of the present invention. When the rate gyro is first placed in operation, triac 21A is biased full on so that capacitor 81 is effectively connected in the motor circuit in parallel with running capacitor 82. As motor 10 builds up in speed, the voltage across resistor 46 increases, and the resulting increase in the positive voltage at the base of transistor 23 drives that transistor to conduction. This decreases the positive voltage on the base of gate transistor 22, which is driven to cut off. Thus, as the motor approaches synchronous speed, triac 21A is driven nonconductive and starting capacitor 81 is effectively cut off from the motor circuit.

In the pickoff excitation and demodulation circuits for the system, comprising multivibrator l6 and demodulator 17, multivibrator 16 is of generally conventional construction, constituting a complementary multivibrator operating at a fixed frequency. Demodulator 17, on the other hand, is substantially different from conventional differential amplifiers and demodulators. Each half of the differential amplifier includes an emitter follower (amplifier transistors 34,39). The external load is that afiorded by the indicating instrument or instruments and represented in FIG. 2 by resistor 20. But the individual emitter followers in demodulator 17 are not of conventional construction. Each includes a polarity-sensitive transistor switching network, afforded by the load transistors 35 and 37.

When the input rate to the gyro is zero, the voltages across the secondary windings 18B and 18C of pickoff transformer 18 are equal. Consequently, the voltages supplied to the base electrodes of transistors 34 and 39 are equal in amplitude and the current in the external load 20 connected to the emitters of these two transistors is zero.

When a turn rate is applied to the gyro, an amplitude differential is created in the AC. analog signals induced in the two secondary windings of pickoff transformer 18. It may be assumed that, for a turn rate input of a given direction, the AC. signal across secondary winding 18B is increased in amplitude in relation to the signal developed across secondary winding 18C. In each cycle of the signals from the pickoff transformer, therefore, the collector-emitter current of transistor 34 is greater than the corresponding current in transistor 39. For a turn rate input of opposite direction, a reverse relation is obtained and the current through transistor 39 exceeds that through transistor 34. Thus, the unbalanced conductivity relationship established in transistors 34 and 39 as the result of application of a turn rate to the gyro develops a DC. current in the external load 20 that is directly proportional to the input turn rate and that has a polarity representative of the direction of the turn rate.

ln demodulator l7, rectification is performed internally in the transistors, particularly amplifier transistors 34 and 39, and adequate demodulation filtering is afforded by capacitor 83. Because the A.C. outputs from the pickoff transformer constitutes a true analog of the turn rate, with amplitude and phase relationships corresponding, respectively, to the rate and the direction of the input to the gyro, the DC. voltage across the external load 20 is a true analog of the input turn rate.

Most of the components of the circuit illustrated in FIG. 2 are preferably constructed as a single unified and integrated circuit. Thus, in the preferred construction for this embodiment of the invention, all of the illustrated circuits for start control 13, inverter 15, multivibrator 16, demodulator 17 and regulator 19 are afforded by a single silicon integrated circuit; the only exceptions, for practical construction, are starting capacitor 81 and resistors 41 and 46, all in start control 13.

We claim:

1. In a rate gyro, a full-wave transformerless A.C. power supply for the spin motor of the gyro, comprising:

a DC. power supply;

an oscillator for generating an initial A.C. signal of given frequency;

a pair of driver amplifiers each comprising a semiconductor switching device;

conductive connection means for applying said initial A.C. signal to said driver amplifiers to develop two synchronous A.C. drive signals of substantially rectangular waveform, at said given frequency;

a pair of bridge switching circuits each including a first semiconductor switching device connected to one terminal of said D.C. power supply, a complementary semiconductor switching device connected to the other terminal of said DC. power supply, and an output terminal connected to both switching devices and to one field winding of said spin motor;

and conductive connection means for applying each of said drive signals to one of said bridge switching circuits to develop a full-wave output signal of generally rectangular waveform at said output terminals.

2. An A.C. power supply for the spin motor of a rate gyro, according to Claim ll, in which said oscillator comprises a self-commutating flip-flop circuit including a pair of parallel input resistors connected to said DC. power supply, a capacitor connected across said input resistors to afford a resistance-capacitance frequency determining input circuit, a pair of silicon bilateral switches individually connected to said input resistors, and a pair of zener diodes individually connected from said bilateral switches back to said DC power supply.

3. An A.C. power supply for the spin motor of a rate gyro, according to Claim 1, in which said A.C. drive si nals are displaced in phase relative to each 0 er and in which said semiconductor switchmg devices comprise transistors all having a single collector supply.

4. An A.C. power supply for the spin motor of a rate gyro, according to claim 3, in which each switching circuit comprises an NPN transistor and a PM? transistor having their emitters connected together at said output terminal, and having their bases connected together and connected to the collector of the driver amplifier transistor and returned to the DC, supply through a load resistor, and in which the collector of the NPN transistor is connected to the positive side of said D.C. supply and the collector of the PNP transistor is connected to the negative side of the DC. supply. 

1. In a rate gyro, a full-wave transformerless A.C. power supply for the spin motor of the gyro, comprising: a D.C. power supply; an oscillator for generating an initial A.C. signal of given frequency; a pair of driver amplifiers each comprising a semiconductor switching device; conductive connection means for applying said initial A.C. signal to said driver amplifiers to develop two synchronous A.C. drive signals of substantially rectangular waveform, at said given frequency; a pair of bridge switching circuits each including a first semiconductor switching device connected to one terminal of said D.C. power supply, a complementary semiconductor switching device connected to the other terminal of said D.C. power supply, and an output terminal connected to both switching devices and to one field winding of said spin motor; and conductive connection means for applying each of said drive signals to one of said bridge switching circuits to develop a full-wave output signal of generally rectangular waveform at said output terminals.
 1. In a rate gyro, a full-wave transformerless A.C. power supply for the spin motor of the gyro, comprising: a D.C. power supply; an oscillator for generating an initial A.C. signal of given frequency; a pair of driver amplifiers each comprising a semiconductor switching device; conductive connection means for applying said initial A.C. signal to said driver amplifiers to develop two synchronous A.C. drive signals of substantially rectangular waveform, at said given frequency; a pair of bridge switching circuits each including a first semiconductor switching device connected to one terminal of said D.C. power supply, a complementary semiconductor switching device connected to the other terminal of said D.C. power supply, and an output terminal connected to both switching devices and to one field winding of said spin motor; and conductive connection means for applying each of said drive signals to one of said bridge switching circuits to develop a full-wave output signal of generally rectangular waveform at said output terminals.
 2. An A.C. power supply for the spin motor of a rate gyro, according to Claim 1, in which said oscillator comprises a self-commutating flip-flop circuit including a pair of parallel input resistors connected to said D.C. power supply, a capacitor connected across said input resistors to afford a resistance-capacitance frequency determining input circuit, a pair of silicon bilateral switches individually connected to said input resistors, and a pair of zener diodes individually connected from said bilateral switches back to said D.C. power supply.
 3. An A.C. power supply for the spin motor of a rate gyro, according to Claim 1, in which said A.C. drive signals are displaced 180* in phase relative to each other and in which said semiconductor switching devices comprise transistors all having a single collector supply. 